Current-controller.



B. l". GARDNER.

CURRENT CONTROLLER.

APPLICATION FILED IuLY24. 191s.

1 287' 952 Patented Dee. 17,1918.

2 SHEETS-SHEET l.

YBIENZJ'AMIIQ FULTON GARDNER, OF CHICAGO, ILLINOIS, ASSIGNOR OF ONE-HALF '10 SEYMOUR STEDMAN,

OF CHICAGO, ILLINOIS.

CURRENT-CONTROLLER.

Specification of Letters Patent.

Patented Dec. 1'?, i912.

To all whom it may concern:

Be it known that I, BENJAMIN FULTON GARDNER, a citizen of the United States, rcsiding at Chicago, in the county of Cook and State of Illinois, have invented a new and useful Improvement in Current-Controllers, of which the following is a specification.

My invention relates means for controlling tric currents. More particularly the invention is concerned with a particular form of adjustable resista-nce member and a convenient unitary housing for the same. rlhe object ofthe invention is to provide a simple and cheap adjustable resistance member of such a form that it may be inserted in a standard lamp or fuse-plug socket, and to provide a unitary mounting in which one or more of suc-h resistance members, together with such fuses as are required for the protection or" the line may be assembled. vThe invention will be more ully understood from the following detailed description, taken in connection with the accompanying drawing, in which* Figure 1 is a top plan view of a bon which servesy yas a base and housing for two of my improved resistance-plugs, and for two fuse-plugs to be arranged in series therewith, the covering being removed.

Fig. 2 is a horizontal section through the Yoox, taken on the line 2 of Fig. 1-, the resistance and fuse-plugs being removed.

Fig.l 3 is a transverse section on the line 3 of Figs. 1 and 2. lig. 4 is a longitudinal section on the line d of Fig. 1, the cover being shown in place.

Fig. 5 is a. section on the to improvements in line 5 of lig. 1;

and

Fig. 6 is an elevation of the two 'faces of a resistance disk.

Referring more particularly to the drawing, the numeral 10 designates the box or housing, which is of generally rectangular form and preferably molded in one piece from porcelain, balrelite or other plastic insulating material. Suitable apertures 11 are formed in the ends of the housing to receive the electrical conductors, and in line with each pair of apertures 11 there are vertically disposed sockets 12, 13, to receive, respectively, the `fuse-plugs and resistance-plugs '"lhe sockets 12, 13 each have seated therein the strength of elecstandard sheet-metal cups 14 having screwthreads pressed in their cylindrical walls, and the bottom of each cup is secured by a washer and cap-screw, which passes downwardly .through an aperture in the base of the socket and is there tapped into a bent conductor 15, which passes from the interior of the housing, through a suitable cored opening, to a recess in the outer face of the housing, the recess being in each instance filled with cement, as designated at 16, after the parts have been assembled, so that the screw sockets form an integral part of the housing' and base. The conductor wires, which are designated 17, are connected to the sockets 12, 13 and through these with each other, as illustrated in Fig. 5.

The upper edge of the housing is rabbeted out, as shown in Figs. et and 5, to provide a shoulder 18, on which the housing coverplate 19 may rest, and the plate is adapted to be secured in position by a screw 20, which engages a nut 21, embedded in cement in a recess in the base oi the housing. Counterbored apertures 22 extend through the base, to receive screws or other fastenings 'by which the housing may be secured to a switchboard or other supporting surface.

The resistance-plug per se is designated as a whole by the numeral 23, and is designed to be screwed into the socket 13. As shown in lig. 5, the shell of the plug is formed of porcelain or other insulating compound, designated 2&1-, and molded into the form oi a cup open at the top and having a perforation through the bottom. The bottom is somewhat conical, as illustrated, and receives a metallic rivet of corresponding `form, the stem of the rivet designated 25 extending through the perforation in the hottom, so that when the plug is in place in the socket it may bear upon the head oi the conductor-screw Above the rivet 25 a plurality of disks oi." suitable diameter to loosely it the interior of the cup are arranged, these disks being alternately metal, (preferably iron) designated 26, and resi tence material, such as carbon or a composition o3.- earthy matter and carhon, designated?. is shown in Fig. 6, one

face of each of the resistance-disks 27 is plane, or Het, and the other iace is cenngated, checkered or otherwise formed to roA ide a plurality of separated Contact pointe.

l the socket. A cap As shown in Fig. 5, there are three disks 274, arranged with their checkered faces downward, and three metal disks 26 which serve to space apart the resistance-units. The cup 24 is closed by an inverted cup in the form of a metal shell 28, which forms screwthreads for coperating with the threads'of 29 is riveted to the shell 28, and an insulating cover 30 is preferably sprung over the cap 29, so that the cap may be grasped for turning the plug without danger of contact with the conducting portions of the plug.

The fuse-plug which occupies the socket 12 is of the standard construction, and requires no description.

When my improved resistance-plug is screwed into its socket, as illustrated in Fig. 5, the stem 25 of the rivet bears upon the head of the conductor-screw in the base of the socket andl thus exerts an upward pressure, forcing together the disks 26 and',27, so that they form contact with the rivet, with one another, and with the head of the shell 28, by which the circuit is completed. Accordingly as the plug is screwed from the end of the socket or loosened, the pressure between the contacting faces of the disks will be varied, and since the largest part of the resistance of the disks is due to their surface contacts, the total resistance of the plug varies correspondingly. By way of example, it may be said that a standard plug of this character has a resistance of the order of 3,000 ohms when it is screwed in loosely, and a resistance as low as 100 ohms when great pressure is Y exerted upon the disks by screwing the plug as firmly as possible into its socket. The checkered or corrugated form of the disk faces I nd to be of great advantage for several reasons. The

large number of point contactsl thus provided increases under light pressures, without proportionately increasing the resistance under heavy pressures, so that the range of resistance obtainable is increased. rlhe checkered surface is further of advantage in that it makes for uniformity of results, since small irregularities in the meeting surfaces of the parts do not cause such marked dierences in the resistance of the plugy nae'aeea resistance of the contact. rThe checkered surface i-s further of advantage in that the disks separate freely as soon as the pressure with plane-surface contacting elements. The Y use of alternate disks of resistance material and metal is of great advantage in that it secures a more uniform result, and further facilitates readjustment of the plug.

The assembled structure comprising a unitary housing which provides a base and socket for the resistance plugs, as well as the fuses, is particularly designed with a view to providing a compact controlling the current in any service line. The cover-plate of the housing may be easily removed at any time to inspect, adjust or replace the plugs and fuses, and when the plate is in place, all operative parts are protected from injury, from interference, vand from accidental short-circuits.

While I have shown and described in con siderable detail one specific embodiment of my invention, it is to be understood that such showing and vdescription is illustrative only and for the purpose of making the invention more clear, and l do not regard the invention as limited to such details nor to any of them, except in so far as such limitations have been included within the' terms of the following claim, in which it is my intention to claim all novelty inherent in my invention as broadly as is permissible in view of the prior art.

What l claim as new and desire t0 secure by Letters Patent is:

A unitary device for Icontrolling the strength of electric currents and comprising a housing member provided with means for leading conductors into and out of the same, a pair of electrically connected plug-sockets mounted within the housing and connected in series, a fuse-plug seated in one of said sockets, a resistance-plug seated in the other socket, resistance members carried by the resistance-plug and controllable by the screwing and unscrewing of the plug, and a cover-plate detachably mounted upon the housing.

BENJAll/HN FTN GARDNER.

and cheap unit for 

